The present disclosure relates to the subject matter disclosed in German Application No. 100 04 470.0 of Feb. 2, 2000, the entire specification of which is incorporated herein by reference.
The invention relates to a process for the milling of a groove into a board-like workpiece by means of a processing machine, wherein the workpiece is placed on a supporting table of the processing machine aligned essentially horizontal for holding the workpiece in a machining plane and wherein a milling unit held on a machining head of the processing machine is displaced and a groove is thereby milled into the workpiece by means of a milling disk rotating about a drive shaft aligned parallel to the machining plane.
The invention relates, in addition, to a processing machine for carrying out the process with a supporting table for holding a board-like workpiece in an essentially horizontal machining plane and with a machining head which can be displaced parallel to the machining plane and on which a milling unit is held, wherein the milling unit comprises a milling disk rotatable about a drive shaft aligned parallel to the machining plane for milling a groove into the workpiece.
Processing machines for the horizontal machining of board-like workpieces, in particular, for the machining of wood or plastic or composite boards or panels enables predetermined grooves to be introduced into the workpiece within a short time with a high reproduction capability. The processing machines are mostly designed as computer-controlled machining centers and comprise a machining head, on which several machining units, for example, drilling and milling units are held. In this respect, milling units with a milling disk, which rotates about a drive shaft aligned parallel to the machining plane, can be used for the milling of V-shaped or U-shaped grooves. The milling unit is held at a predeterminable distance in relation to the workpiece to be machined and displaced parallel to the machining plane in a computer-controlled manner.
In order to be able to make a groove with a constant groove depth in this manner it is necessary for the upper side of the workpiece to be machined, which faces the milling disk, to be aligned exactly parallel to the advancing direction of the milling disk. For this purpose, considerable attempts have been made with conventional processing machines to align the supporting table and the advancing direction of the machining head and of the milling disk exactly parallel to one another. It has, however, been shown that despite such an alignment grooves with a groove depth remaining constant in the advancing direction cannot, in all cases, be milled into board-like workpieces.
The object of the present invention is to make a process of the type described at the outset available which makes the more precise milling of a groove into a board-like workpiece with a defined groove depth possible.
This object is accomplished in accordance with the invention, in a process of the generic type, in that the milling unit is guided at right angles to the direction of machining by means of a touch roller associated with the milling disk and adapted to roll on the workpiece. With such a procedure, the distance of the milling unit to the workpiece transversely to the machining plane is defined by the touch roller which rolls on the upper side of the workpiece facing the milling unit. For this purpose, the milling unit is held on the machining head so as to be displaceable transversely to the machining plane, i.e. its distance to the machining plane is not rigidly specified but rather is dependent on the positioning of the touch roller and thus on the path of the upper side of the workpiece to be machined. Any non-parallelisms between the upper side of the workpiece and the guidance of the milling unit can thus be reliably prevented. This makes the extremely precise milling of a groove with a defined groove depth possible, which has an effect, in particular, for the machining of multilayered or composite boards which are intended to be deformed after the groove has been made. Multilayered boards normally comprise a center layer consisting of a plastic or a material on a mineral basis which is difficult to bend, i.e. can be bent only with a large bending radius, the center layer being covered on its upper side and its lower side by a mostly metallic cover layer capable of bending. Multilayered boards of this type may be folded xe2x80x9cby handxe2x80x9d in a simple manner in that a V-shaped or rectangular groove is milled first of all along the bending edge by means of a form cutter, wherein after the groove has been made the remaining material has only a very slight thickness of, for example, 0.8xc2x10.1 mm. Subsequently, the multilayered board can be folded by hand without a folding machine or the like being required for this purpose. A precondition for this is, however, that the depth of the groove is maintained very precisely over the entire length of the groove. The same applies for boards or panels consisting of a composite material, for example, of a plastic material, with which mineral substances have been mixed. Composite materials of this type are likewise very hard to bend, wherein only large bending radii can be achieved. Even small bending radii can, however, be achieved when the composite boards are provided first of all with a very precise groove, as has already been explained above in the case of multilayered boards.
It is of advantage when chips located immediately in front of the touch roller in the advancing direction of the milling unit are removed from the contact area of the touch roller by means of an air nozzle. In this way, chips located on the upper side of the workpiece can be reliably prevented from influencing the positioning of the touch roller rolling on the upper side of the workpiece and thus of the milling disk. A particularly precise groove can be milled in a reproducible manner as a result of the chips being removed.
The removal of the chips can take place in that these are drawn off by means of a suction unit. A procedure has proven to be particularly reliable, with which the chips are removed by means of a blast nozzle, i.e. they are blown away from the contact area of the touch roller by means of a flow of air. In this respect, it is particularly favorable when the chips blown away are subsequently drawn off by suction.
The object underlying the invention is, in addition, to make a processing machine of the type specified at the outset available for carrying out the process.
This object is accomplished in a processing machine of the generic type in that the milling unit is held on the machining head so as to be continuously displaceable at right angles to the machining plane during the introduction of a groove and that a touch roller which can roll on the workpiece is associated with the milling disk for guiding the milling unit, wherein the milling disk projects beyond the edge of the touch roller by the depth of the groove in the contact area of the touch roller on the workpiece.
With a processing machine of this type the milling unit can be displaced by means of conventional drive elements parallel to the machining plane along predeterminable coordinates. The positioning of the milling unit at right angles to the machining plane is predetermined by the touch roller rolling on the workpiece and so the milling unit can be displaced at a very precise distance in relation to the upper side of the workpiece.
As the milling disk projects beyond the touch roller, the depth of the groove is predetermined precisely by the distance of the outer edge of the milling disk from the corresponding edge of the touch roller.
It is favorable when the projection of the milling disk beyond the edge of the touch roller in the contact area of the touch roller on the workpiece can be adjusted. This makes the use of a touch roller for different groove depths possible in that the distance of the touch roller in the contact area on the workpiece from the outer edge of the milling disk can be adjusted accordingly.
In a particularly preferred development of the processing machine it is provided for the touch roller to comprise a freely rotatable touch ring which can be abutted on the workpiece and is held so as to be adjustable transversely to the drive shaft of the milling disk. The positioning of the axis of rotation of the touch roller relative to the position of the drive shaft of the milling disk can thus be altered transversely to the machining plane. This makes it possible to alter the projection of the outer edge of the milling disk in relation to the edge of the touch roller in the contact area of the touch roller on the workpiece in a simple manner. If the milling disk is reground so that its diameter is changed, the distance of the outer edge of the milling disk in relation to the touch roller can be readjusted in that the touch ring is repositioned accordingly relative to the milling disk. Such a repositioning makes possible, in addition, an adjustment of the depth of the groove to workpiece thickness tolerances.
In order to achieve a particularly precise groove depth, it is of advantage when the milling unit comprises an air nozzle directed onto the contact area of the touch roller on the workpiece. A flow of air can be generated by means of the air nozzle in the contact area of the touch roller on the workpiece for removing chips resting on the upper side of the workpiece.
In this respect, it is particularly favorable when the air nozzle is designed as a blast nozzle which can be connected to a source of compressed air via a pressure line.
In a particularly preferred development of the inventive processing machine it is provided for the milling unit to comprise a suction hood which surrounds the milling disk and the touch roller and is in flow communication with a suction unit via a suction line.
Chips resulting during milling can thus be drawn off reliably. In this respect, it is particularly favorable when the suction hood surrounds the mouth area of the blast nozzle. Resulting chips can be removed from the contact area of the touch roller by means of the blast nozzle, wherein it is ensured at the same time on account of the suction nozzle that these are subsequently drawn off via the suction line.
As already explained above, the processing machine is suitable, in particular, for the precise milling of a preferably V-shaped or U-shaped groove into a multilayered board which comprises at least two layers with different bending stiffnesses or also into boards consisting of composite materials. In the case of multilayered boards, a groove can be milled into the layer more resistant to bending so that, subsequently, the multilayered board can be deformed by hand in the area of the layer having a lesser bending stiffness. Multilayered boards suitable for this purpose have, in particular, an intermediate layer and cover layers which cover the upper and lower sides of the intermediate layer, wherein the intermediate layer has a greater bending stiffness than the cover layers. It may, for example, be provided for the intermediate layer to be manufactured from a plastic material or a material on a mineral basis. A metal layer, in particular, an aluminum layer can preferably be used for the cover layer.